Inhibition of the pyridine nucleotide-linked mitochondrial Ca(2+) release by 4-hydroxynonenal: the role of thiolate-disulfide conversion.

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Rat liver mitochondria contain a specific Ca(2+) release pathway which operates when intramitochondrial NAD(+) is hydrolyzed to ADPribose and nicotinamide. The molecular details of this pathway are incompletely understood. It has been reported that NAD(+) hydrolysis and therefore Ca(2+) release stimulated by t-butylhydroperoxide is prevented by 4-hydroxynonenal (HNE). The reason underlying inhibition by HNE, however, remained unclear. It has also been reported that NAD(+) hydrolysis and Ca(2+) release are stimulated when some vicinal thiols are cross-linked, as shown with phenylarsine oxide or gliotoxin (GT). We now show that HNE also prevents the GT-induced Ca(2+) release, but only when given before GT. Conversely, GT stimulates Ca(2+) release only when given before HNE. Inhibition of Ca(2+) release by HNE is reduced by its preincubation with thiol compounds, the effectiveness of which increases with decreasing pKa of their sulfhydryl group. Preincubation of HNE with glutathione at high, but not at low, pH similarly reduces inhibition of Ca(2+) release by HNE. These findings provide evidence that HNE inhibition of Ca(2+) release is due to a modification of mitochondrial thiolates in a way that their cross-linking is prevented, and give further insight into the regulation of Ca(2+) release from intact mitochondria.